But it’s easy to imagine a bouncer at a club with a list of whites allowed in and blacks that aren’t. I don’t think that’s the etymology, but it’s also important to remember that language is alive and words can take on unintended meaning.

that seems like an oddly specific origination for that specific term, but it’s certainly a possibility. But as with words being alive and taking on unintended meanings, it’s also equally likely that it became skin color agnostic at some point, and the term stuck because it was already being used.